Can we get clarity regarding Minion agro and autos vs on hits?

So I first heard that minion aggro is drawn when you auto attack an enemy champion, and when I found out Ezreal and GP Qs drew it, I assumed it was considered an on hit effect. Except Azir soldiers proc it (soldiers do not proc on hit effects, only spell effects). Which would suggest it is not an on hit and in fact an auto attack effect. But then why would Ez and GP Qs draw aggro?

My main issue with minions is our information is so inconsistent and/or vague. "Break line of sight to drop aggro" day 437 running back to base putting as many units between myself and minions as possible. They are still aggro'd.

etc etc. Also obligatory "Why the fuck can our own minions block us" comment